1. Field of the Invention
The present invention relates to a centrifugal pump.
2. Description of the Prior Art
In the centrifugal pump of U.S. Pat. No. 3,795,459 the liquid is delivered centrally into a rotor and centrifugally accelerated in a feed chamber of the rotor. On the rotor circumference the liquid flows into a discharge chamber positioned axially behind it. Close to the inner circumference of the discharge chamber the accelerated liquid is removed by a scoop pipe, which converts the kinetic and static energy substantially into pressure energy, and is coaxially discharged on the pressure side. These known centrifugal scoop pipe pumps operate in the overpressure range with a complete filling of the discharge chamber and high rotor speeds. On the feed side they require at least atmospheric pressure or overpressure.
A pump disclosed in U. S. Pat. No. 4,171,182 operates with which liquid being discharged from an underpressure or vacuum chamber. A rotor rotates in a tight casing and has several delivery ducts extending outwards from the center and to whose outlet is in each case connected a short, siphon-like deflection or return with an overflow. The liquid supplied in the center of the rotor is centrifugally accelerated into the delivery ducts and inwardly deflected at the outlet thereof. At the overflow of the siphon-like deflection, the liquid runs out into the casing and is tangentially discharged from the latter. By means of a centrally introduced line, the rotor is connected to the vacuum chamber, so that there is a pressure compensation between the vacuum chamber and the low pressure side of the pump. Sealing between the interior of the rotor and the pressure side takes place by the siphon-like deflection, in much the same way as in a liquid seal pump.
It is disadvantageous in this known pump, that the sealing of the vacuum chamber is only ensured by the liquid in the siphon-like deflection or return. In the case of foaming or boiling liquids, as with suddenly occurring pressure surges, there is consequently a risk of a gas escape or air leak. The delivery of highly viscous or solids-containing liquids is also problematical.
The invention provides a centrifugal pump which operates to discharge liquids from process equipment with vacuum and, as a result, the aforementioned disadvantages do not arise.